4. Alsamixer is sometimes muted by default, so you might need to unmute it. Run alsamixer:

alsamixer

Use arrows up and down to change volume, left and right to change source. To mute/unmute press M.

Note: Alsamixer might look different in any machine. It depends on your sound device (sound card). Please, read audio source labels. For example: PCM in Virtualbox is on fifth place instead of the second in VMWare.